Detection of marked mineral oils and novel azo dyes

ABSTRACT

Method for detecting marked mineral oils by treating the marked mineral oil with an extractant comprising water, a solvent and a base comprises using as marker an azo dye of the formula ##STR1## where ring A may be benzofused, 
     m is from 1 to 4, 
     X 1  is hydrogen, C 1  -C 4  -alkyl, cyano or nitro, 
     X 2  is hydrogen, C 1  -C 4  -alkyl, cyano, nitro, C 1  -C 4  -alkoxy or C 1  -C 16  -alkoxycarbonyl, 
     X 3  is hydrogen, C 1  -C 4  -alkyl, cyano or C 1  -C 16  -alkoxycarbonyl, and 
     X 4  is hydrogen, hydroxyl, substituted or unsubstituted C 1  -C 8  -alkyl, C 1  -C 4  -alkoxy, amino, C 1  -C 4  -dialkylamino or substituted or unsubstituted C 1  -C 16  -monoalkylamino, 
     as solvent a partially or completely water-miscible organic solvent, and as base an alkali or alkaline earth metal hydroxide, an alkali metal carbonate or a quaternary ammonium hydroxide, the use of azo dyes as markers for mineral oils, and novel azo dyes.

The present invention relates to a novel method for detecting azo dye marked mineral oils, the use of monoazo or disazo dyes as markers for mineral oils, and novel azo dyes.

U.S. Pat. No. 5,156,653 discloses the use of phenylazophenols for marking mineral oils. The markers are detected there by shaking the marked mineral oil with a mixture of water, diethylene glycol and methoxyethoxypropylamine to form a mineral oil phase and an aqueous phase containing the azo dye. However, it has been found that the method of detection described there is not satisfactory. It does not have universal utility and frequently produces only an extremely weak coloring of the aqueous phase, since some of the dye used remains in the oil phase.

U.S. Pat. No. 3,764,273 describes the extraction of quinizarin derivatives and of specific azo dyes, inter alia with aqueous alkali and dimethyl sulfoxide.

Finally, U.S. Pat. No. 5,252,106 discloses the use of 4-(4'-phenylazophenylazo)phenols for marking mineral oils.

It is an object of the present invention to provide a novel method for detecting azo dye marked mineral oils which is simple to carry out and by means of which the markers, even in low concentrations, can be visibilized by strong color reaction.

We have found that this object is achieved by a method for detecting azo dye marked mineral oils by treating the marked mineral oil with an extractant comprising water, a solvent and a base, the azo dye transferring from the mineral oil into the aqueous phase, which comprises using as marker an azo dye of the formula I ##STR2## where ring A may be benzofused,

m is from 1 to 4,

X¹ is hydrogen, C₁ -C₄ -alkyl, cyano or nitro,

X² is hydrogen, C₁ -C₄ -alkyl, cyano, nitro, C₁ -C₄ -alkoxy or C₁ -C₁₆ -alkoxycarbonyl,

X³ is hydrogen, C₁ -C₄ -alkyl, cyano or C₁ -C₁₆ -alkoxycarbonyl, and

X⁴ is hydrogen, hydroxyl, C₁ -C₈ -alkyl, which may be phenyl-substituted, C₁ -C₄ -alkoxy, amino, C₁ -C₄ -dialkylamino or C₁ -C₁₆ -monoalkylamino whose alkyl chain may be interrupted by from 1 to 3 oxygen atoms in the ether function,

as solvent a partially or completely water-miscible organic solvent, and as base an alkali or alkaline earth metal hydroxide, an alkali metal carbonate or an ammonium compound of the formula ##STR3## where R¹, R², R³ and R⁴ are each independently of the others C₁ -C₁₆ -alkyl or benzyl.

Any alkyl appearing in the abovementioned formulae may be straight-chain or branched.

Unless otherwise stated, substituents in substituted phenyl or naphthyl appearing in the abovementioned formula need not all be the same.

X¹, X², X³, X⁴, R¹, R², R³ and R⁴ are each for example methyl, ethyl, propyl, isopropyl, butyl, isobutyl or sec-butyl.

X⁴, R¹, R², R³ and R⁴ may each also be for example pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, 2-methylpentyl, heptyl, octyl, 2-ethylhexyl or isooctyl.

R¹, R², R³ and R⁴ may each also be for example nonyl, isononyl, decyl, isodecyl, undecyl, dodecyl, tridecyl, 3,5,5,7-tetramethylnonyl, isotridecyl, tetradecyl, pentadecyl or hexadecyl (the above designations isooctyl, isononyl, isodecyl and isotridecyl are trivial names derived from the oxo process alcohols - cf. Ullmanns Encyclopadie der technischen Chemie, 4th edition, Volume 7, pages 215 to 217, and Volume 11, pages 435 and 436).

X⁴ may also be for example dimethylamino, diethylamino, dipropylamino, diisopropylamino, dibutylamino, methylamino, ethylamino, propylamino, isopropylamino, butylamino, isobutylamino, sec-butylamino, pentylamino, isopentylamino, neopentylamino, tert-pentylamino, hexylamino, 2-methylpentylamino, heptylamino, octylamino, 2-ethylhexylamino, isooctylamino, nonylamino, isononylamino, decylamino, isodecylamino, undecylamino, dodecylamino, tridecylamino, 3,5,5,7-tetramethylnonylamino, isotridecylamino, tetradecylamino, pentadecylamino, hexadecylamino, 2-methoxyethylamino, 2-ethoxyethylamino, 2-methoxypropylamino, 3,6-dioxaheptylamino, 3,6-dioxaoctylamino, 3,6,9-trioxadecylamino, 3,6,9-trioxaundecylamino, benzyl or 1- or 2-phenylethyl.

X² and X⁴ may each also be for example methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy or sec-butoxy.

X² and X³ may each also be for example methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, isobutoxycarbonyl, sec-butoxycarbonyl, pentyloxycarbonyl, isopentyloxycarbonyl, neopentyloxycarbonyl, tert-pentyloxycarbonyl, hexyloxycarbonyl 2-methylpentyloxycarbonyl, heptyloxycarbonyl, octyloxycarbonyl, 2-ethylhexyloxycarbonyl, isooctyloxycarbonyl, nonyloxycarbonyl, isononyloxycarbonyl, decyloxycarbonyl, isodecyloxycarbonyl, undecyloxycarbonyl, dodecyloxycarbonyl, tridecyloxycarbonyl, isotridecyloxycarbonyl, tetradecyloxycarbonyl, pentadecyloxycarbonyl or hexadecyloxycarbonyl.

Attention is drawn in particular to a method of detection using azo dyes of the formula I where

X¹ is hydrogen or C₁ -C₄ -alkyl,

X² is hydrogen, C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy or C₁ -C₁₆ -alkoxycarbonyl,

X³ is hydrogen, C₁ -C₄ -alkyl, or C₁ -₁₆ -alkoxycarbonyl, and

m, Y and X⁴ are each as defined above.

Particular preference is given to using in the method of the invention azo dyes of the formula Ia ##STR4## where m is from 1 to 4,

X¹ is hydrogen, cyano or nitro,

X² is hydrogen, C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy or C₁ -C₁₃ -alkoxycarbonyl,

X³ is hydrogen or C₁ -C₄ -alkyl, and

X⁴ is hydrogen or C₁ -C₄ -alkyl, which may be phenyl-substituted.

Particular preference is further given to using in the method of the invention azo dyes of the formula Ib ##STR5## where X¹ is hydrogen,

X² is hydrogen,

X³ is hydrogen or C₁ -C₄ -alkyl,

X⁴ is hydrogen, C₁ -C₄ -alkyl, C₁ -C₄ -dialkylamino or C₁ -C₁₆ -monoalkylamino,

X⁵ is hydrogen or C₁ -C₄ -alkyl, and

X⁶ is hydrogen, C₁ -C₄ -alkyl or C₁ -C₄ -alkoxy,

with the proviso that a) at least one of the three radicals X¹, X² and X³ is different from hydrogen, b) X² may also be cyano when X⁴ is C₁ -C₄ -dialkylamino, c) X² may also be C₁ -C₄ -alkoxycarbonyl when all the radicals X⁴, X⁵ and X⁶ are different from hydrogen, and d) one of the radicals X¹, X² or X³ may also be nitro when X⁴ is C₁ -C₁₆ -monoalkylamino and X⁶ is C₁ -C₄ -alkyl.

Very particular preference is given to using in the method of the invention azo dyes of the formula Ia where X⁴ is hydrogen or 1-phenylethyl.

Very particular preference is further given to using in the method of the invention azo dyes of the formula Ia where X¹ is hydrogen, X² is methyl or C₁ -C₁₃ -alkoxycarbonyl, and X³ is hydrogen or methyl.

Suitable alkali or alkaline earth metal hydroxides or alkali metal carbonates for use in the method of the invention include for example lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, lithium carbonate, sodium carbonate and potassium carbonate.

Suitable ammonium compounds include for example tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, benzyltriethylammonium hydroxide and benzyltributylammonium hydroxide.

The use of alkali or alkaline earth metal hydroxides as base is preferred with particular attention being drawn to alkali metal hydroxides.

Particular preference is given to the use of lithium hydroxide, sodium hydroxide or potassium hydroxide as base, sodium hydroxide being of particular importance.

Since the extractant includes water, the alkali or alkaline earth metal hydroxides, alkali metal carbonates or ammonium compounds are preferably used directly in the form of an aqueous solution, this aqueous solution generally having an alkali or alkaline earth metal hydroxide, alkali metal carbonate or ammonium compound content from 0.1 to 10% by weight, preferably from 1 to 10% by weight, each percentage being based on the weight of the aqueous solution.

Suitable solvents are partially or completely water-miscible organic solvents. This includes for example amides, especially carboxamides, such as formamide, N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, pyrrolidin-2-one, 1-methylpyrrolidin-2-one (NMP), 1,3-dimethylhexahydropyrimid-2-one or hexamethylphosphoramide, N,N,N',N'-tetramethylguanidine, acetonitrile, nitromethane, amines, such as 2-aminoethanol, 1,10-diamino-4,7-dioxadecane, 1,13-diamino-4,7,10-trioxatridecane, 2- or 3-methoxypropylamine, 1,8-bis(dimethylamino)naphthalene or an amine of the formula H₂ N--CH(CH₃)CH₂ [--OCH(CH₃)CH₂ ]₂,6 --OCH₂ CH--(CH₃)--NH₂, 1-methylpyrazole, dimethyl sulfoxide (DMSO) or sulfolane.

Preferred solvents are 1-methylpyrazole, pyrrolidin-2-one, 1-methylpyrrolidin-2-one, dimethyl sulfoxide and sulfolane.

In some cases it can also be of advantage for the extractant to include further admixtures, for example 4-nonylphenol, or for the mineral oil to have 4-nonylphenol added to it prior to the extraction.

Based on the weight of the extractant, the proportion of solvent typically ranges from 50 to 99% by weight, preferably from 90 to 99% by weight.

To mark mineral oil, the azo dyes of the formula I are used either without a solvent or in the form of solutions. Suitable solvents include preferably aromatic hydrocarbons, such as toluene, xylene, dodecylbenzene, diisopropylnaphthalene or a mixture of higher aromatics commercially available from Shell as Shellsol® AB. The solubility may be improved in a conventional manner by using further, co-solvents, for example alcohols, such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, hexanol, heptanol, octanol, 2-ethylhexanol or cyclohexanol, glycols, such as butylethylene glycol or methylpropylene glycol, amines, such as triethylamine, diisooctylamine, dicyclohexylamine, aniline, N-methylaniline, N,N-dimethylaniline, toluidine or xylidine, alkanolamines, such as 3-(2-methoxyethoxy)propylamine, o-cresol, m-cresol, p-cresol, ketones, such as diethyl ketone or cyclohexanone, lactams, such as γ-butyrolactam, carbonates, such as ethylene carbonate or propylene carbonate, phenols, such as t-butylphenol or nonylphenol, esters, such as methyl phthalate, ethyl phthalate, 2-ethylhexyl phthalate, ethyl acetate, butyl acetate or cyclohexyl acetate, amides, such as N,N-dimethylformamide, N,N-diethylacetamide or N-methylpyrrolidin-2-one, or mixtures thereof. To avoid the resulting solution from becoming too viscous, it is generally advisable to use a concentration of azo dye I from 1 to 50% by weight, preferably from 10 to 50% by weight, each percentage being based on the solution.

In the course of the treatment of the marked mineral oil with the extractant, for example by shaking, the azo dye of the formula I transfers into the aqueous phase, which takes on a distinctly visible color in the process.

The method of the invention provides a very simple means of detecting mineral oils marked with azo dyes of the formula I. A further advantage of the method of the invention is that it permits the extraction of dyes which have only little acidity.

The present invention further provides for the use of azo dyes of the abovementioned formulae Ia and Ib for marking mineral oils.

Preference for marking mineral oils is given to the use of azo dyes of the formula Ia where X⁴ is hydrogen or 1-phenylethyl.

Preference for marking mineral oils is further given to the use of azo dyes of the formula Ia where X¹ is hydrogen, X² is methyl or C₁ -C₁₃ -alkoxycarbonyl, and X³ is hydrogen or methyl.

Particular preference for marking mineral oils is further given to the use of azo dyes of the formula Ic ##STR6## where Y is C₇ -C₁₁ -alkyl.

Mineral oils for the purposes of the present invention include for example motor fuels, such as gasoline, kerosine or diesel fuel, or oils, such as fuel oil or engine oil.

The azo dyes of the formula Ia or Ib are especially suitable for marking mineral oils where a form of identification is required, for example for tax reasons. To keep the costs for this to a minimum, it is desirable to keep the amount of marker used to a minimum.

Marking for the purposes of the present invention is the addition of the azo dyes of the formula Ia or Ib to mineral oils in such a concentration that, to the human eye, the mineral oils have barely any or no visible color, although the dyes of the formulae Ia and Ib are readily and distinctly visibly detectable by the methods of detection more particularly described herein.

To mark mineral oil, the azo dyes of the formula Ia or Ib, as mentioned above, are used either without a solvent or in the form of solutions.

The azo dyes of the formula Ia or Ib to be used according to the invention have the advantage of being suitable, depending on their concentration, of conferring a clearly visible color on mineral oils and/or for use as marker substances.

The azo dyes of the formula Ia or Ib to be used according to the invention permit very simple detection of marked mineral oils, even if the marker substances are present only in a concentration of about 10 ppm or less.

The azo dyes of the formula Ia have the application advantage of very good solubility and also excellent dilutability. Moreover, in the detection reaction, they give distinctly more bathochromic hues than the dyes known from U.S. Pat. No. 5,156,653.

It is a further object of the present invention to provide novel azo dyes which shall be advantageous for use as marker substances for mineral oils.

We have found that this object is achieved by the azo dyes of the formula II ##STR7## where Y¹ is hydrogen, or C₁ -C₄ -alkyl-substituted phenylazo,

Y² is hydrogen,

Y³ is hydrogen or C₁ -C₄ -alkyl,

X⁴ is hydrogen, C₁ -C₄ -alkyl, C₁ -C₄ -dialkylamino or C₁ -C₁₆ -monoalkylamino,

X⁵ is hydrogen or C₁ -C₄ -alkyl, and

X⁶ is hydrogen, C₁ -C₄ -alkyl or C₁ -C₄ -alkoxy,

with the proviso that a) at least one of the three radicals Y¹, Y² and Y³ is different from hydrogen, b) Y² may also be cyano when X⁴ is C₁ -C₄ -dialkylamino, c) Y² may also be C₁ -C₄ -alkoxycarbonyl when all the radicals X⁴, X⁵ and X⁶ are different from hydrogen, and d) one of the radicals Y¹, Y² or Y³ or may also be nitro when X⁴ is C₁ -C₁₆ -monoalkylamino and X⁶ is C₁ -C₄ -alkyl.

Preference is given to azo dyes of the formula II where Y¹ is hydrogen.

The novel azo dyes of the formula II are obtainable in a conventional manner, for example by diazotizing an aniline of the formula III ##STR8## where Y¹, Y² and Y³ are each as defined above, and coupling the resulting diazonium compound with a phenol of the formula IV ##STR9## where X⁴, X⁵ and X⁶ are each as defined above.

The further azo dyes of the formula I and those of the formula Ia are generally compounds known per se. They are described for example in U.S. Pat. No. 5,156,653 or U.S. Pat. No. 4,473,376 or can be obtained by the methods mentioned therein.

The Examples which follow illustrate the invention (parts are by weight).

EXAMPLE 1

Commercial diesel fuel was admixed with 10 ppm of a dye (F1) of the formula ##STR10##

9 parts of the diesel fuel thus marked red were admixed with 0.5 part of a mixture of 4 parts of distilled water, 4 parts of 1,10-diamino-4,7-dioxadecane and 2 parts of 10% strength by weight sodium hydroxide solution and vigorously shaken. After about 1 min an aqueous phase with a strong red color separated off as bottom layer. The supernatant diesel fuel phase was almost colorless. The coloring of the aqueous phase was unchanged after 24 h at room temperature.

A blank test carried out on unmarked diesel oil under similar conditions produced an aqueous phase which was almost colorless.

Performing the reaction under similar conditions with a commercial gasoline (from Aral) marked with the dye F1 produced the same color effect as was obtained in the case of marked diesel fuel.

A blank test carried out on unmarked gasoline (from Aral) under similar conditions produced an aqueous phase which was almost colorless.

Similar detection results were achieved on diesel fuel marked with the dyes listed below using various reagent solutions likewise listed below.

Dyes: ##STR11## Reagent solutions: R1 9 parts of NMP and 1 part of 1% strength by weight aqueous lithium hydroxide solution

R2 9 parts of 2-pyrrolidinone and 1 part of 1% strength by weight aqueous lithium hydroxide solution

R3 9 parts of DMSO and 1 part of 2% strength by weight aqueous lithium hydroxide solution

R4 9.5 parts of 1-methylimidazole and 0.5 part of 5% strength by weight aqueous lithium hydroxide solution

R5 9.5 parts of amine of formula H₂ N--CH(CH₃)CH₂ [--OCH(CH₃)CH₂ ]₂,6 --OCH₂ CH(CH₃)--NH₂ and 0.5 part of 1% strength by weight aqueous lithium hydroxide solution

R6 9 parts of 1,3-dimethylhexahydropyrimid-2-one and 1 part of 1% strength by weight aqueous lithium hydroxide solution

R7 9 parts of 1,13-diamino-4,7,10-trioxatridecane and 1 part of 1% strength by weight aqueous lithium hydroxide solution

R8 5 parts of 3-methoxypropylamine and 1 part of 5% strength by weight aqueous potassium hydroxide solution

R9 4 parts of distilled water, 4 parts of 1,10-diamino-4,7-dioxadecane and 2 parts of 10% strength by weight sodium hydroxide solution

R10 9 parts of DMSO, 1 part of 2% strength by weight aqueous lithium hydroxide solution and 1 part of 4-nonylphenol

The following results were obtained:

    ______________________________________                                                                    Hue of Hue of Marker                                                           oily   oily   concen-                                                   Hue of phase  phase  tration                               Ex.         Re-     aqueous                                                                               after  before in diesel                             No.  Dye    agent   phase  shaking                                                                               shaking                                                                               fuel                                  ______________________________________                                          2   F1     R1      strongly                                                                              colorless                                                                             strongly                                                                              10 ppm                                                    red           yellow                                        3   F1     R2      strongly                                                                              colorless                                                                             strongly                                                                              10 ppm                                                    red           yellow                                        4   F1     R3      strongly                                                                              colorless                                                                             strongly                                                                              10 ppm                                                    red           yellow                                        5   F1     R4      strongly                                                                              colorless                                                                             strongly                                                                              10 ppm                                                    red           yellow                                        6   F1     R8      weakly weakly strongly                                                                              10 ppm                                                    red    yellow yellow                                        7   F1     R10     strongly                                                                              almost strongly                                                                              10 ppm                                                    red    colorless                                                                             yellow                                        8   F2     R1      strongly                                                                              colorless                                                                             strongly                                                                               5 ppm                                                    orange        orange                                        9   F2     R2      strongly                                                                              colorless                                                                             strongly                                                                               5 ppm                                                    orange        orange                                        10  F2     R3      strongly                                                                              almost strongly                                                                               5 ppm                                                    orange colorless                                                                             orange                                        11  F2     R4      yellowish                                                                             weakly strongly                                                                               5 ppm                                                    orange yellow orange                                        12  F2     R5      strongly                                                                              colorless                                                                             strongly                                                                               5 ppm                                                    orange        orange                                        13  F2     R6      strongly                                                                              slightly                                                                              strongly                                                                               5 ppm                                                    orange yellow orange                                        14  F2     R7      strongly                                                                              colorless                                                                             strongly                                                                               5 ppm                                                    orange        orange                                        15  F2     R8      strongly                                                                              almost strongly                                                                               5 ppm                                                    orange colorless                                                                             orange                                        16  F2     R9      orange slightly                                                                              strongly                                                                               5 ppm                                                           yellow orange                                        17  F2     R10     strongly                                                                              almost strongly                                                                               5 ppm                                                    orange colorless                                                                             orange                                        18  F3     R1      strongly                                                                              almost strongly                                                                               5 ppm                                                    orange colorless                                                                             orange                                        19  F3     R2      strongly                                                                              colorless                                                                             strongly                                                                               5 ppm                                                    orange        orange                                        20  F3     R3      strongly                                                                              almost strongly                                                                               5 ppm                                                    orange colorless                                                                             orange                                        21  F3     R4      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange orange orange                                        22  F3     R5      strongly                                                                              colorless                                                                             strongly                                                                               5 ppm                                                    orange        orange                                        23  F3     R6      strongly                                                                              almost strongly                                                                               5 ppm                                                    orange colorless                                                                             orange                                        24  F3     R7      strongly                                                                              colorless                                                                             strongly                                                                               5 ppm                                                    orange        orange                                        25  F3     R8      orange weakly strongly                                                                               5 ppm                                                           orange orange                                        26  F3     R9      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange orange orange                                        27  F3     R10     strongly                                                                              almost strongly                                                                               5 ppm                                                    orange colorless                                                                             orange                                        28  F4     R1      strongly                                                                              colorless                                                                             strongly                                                                              10 ppm                                                    red           yellow                                        29  F4     R2      strongly                                                                              colorless                                                                             strongly                                                                              10 ppm                                                    red           yellow                                        30  F4     R3      strongly                                                                              almost strongly                                                                              10 ppm                                                    red    colorless                                                                             yellow                                        31  F4     R8      yellow weakly strongly                                                                              10 ppm                                                           yellow yellow                                        32  F4     R9      weakly weakly strongly                                                                              10 ppm                                                    yellow yellow yellow                                        33  F4     R10     strongly                                                                              weakly strongly                                                                              10 ppm                                                    yellow yellow yellow                                        34  F5     R1      strongly                                                                              slightly                                                                              strongly                                                                              10 ppm                                                    orange yellow yellow                                        35  F5     R2      strongly                                                                              slightly                                                                              strongly                                                                              10 ppm                                                    orange yellow yellow                                        36  F5     R3      strongly                                                                              almost strongly                                                                              10 ppm                                                    orange colorless                                                                             yellow                                        37  F5     R8      yellow weakly strongly                                                                              10 ppm                                                           yellow yellow                                        38  F5     R9      weakly weakly strongly                                                                              10 ppm                                                    yellow yellow yellow                                        39  F5     R10     strongly                                                                              weakly strongly                                                                              10 ppm                                                    orange orange yellow                                        40  F6     R1      strongly                                                                              colorless                                                                             strongly                                                                              10 ppm                                                    orange        yellow                                        41  F6     R2      strongly                                                                              colorless                                                                             strongly                                                                              10 ppm                                                    orange        yellow                                        42  F6     R3      strongly                                                                              almost strongly                                                                              10 ppm                                                    orange colorless                                                                             yellow                                        43  F6     R8      strongly                                                                              almost strongly                                                                              10 ppm                                                    red    colorless                                                                             yellow                                        44  F6     R9      strongly                                                                              weakly strongly                                                                              10 ppm                                                    red    yellow yellow                                        45  F6     R10     strongly                                                                              almost strongly                                                                              10 ppm                                                    red    colorless                                                                             yellow                                        46  F7     R1      strongly                                                                              slightly                                                                              strongly                                                                               5 ppm                                                    red    yellow yellow                                        47  F7     R2      strongly                                                                              almost strongly                                                                               5 ppm                                                    red    colorless                                                                             yellow                                        48  F7     R3      strongly                                                                              almost strongly                                                                               5 ppm                                                    reddish                                                                               colorless                                                                             yellow                                                           violet                                                      49  F7     R8      strongly                                                                              almost strongly                                                                               5 ppm                                                    red    colorless                                                                             yellow                                        50  F7     R9      strongly                                                                              weakly strongly                                                                               5 ppm                                                    red    yellow yellow                                        51  F7     R10     strongly                                                                              almost strongly                                                                               5 ppm                                                    red    colorless                                                                             yellow                                        52  F8     R1      strongly                                                                              almost strongly                                                                              20 ppm                                                    orange colorless                                                                             yellow                                        53  F8     R2      strongly                                                                              almost strongly                                                                              20 ppm                                                    orange colorless                                                                             yellow                                        54  F8     R3      strongly                                                                              almost strongly                                                                              20 ppm                                                    orange colorless                                                                             yellow                                        55  F8     R8      strongly                                                                              weakly strongly                                                                              20 ppm                                                    orange yellow yellow                                        56  F8     R9      weakly weakly strongly                                                                              20 ppm                                                    yellow yellow yellow                                        57  F8     R10     strongly                                                                              slightly                                                                              strongly                                                                              20 ppm                                                    orange yellow yellow                                        58  F9     R1      orange weakly yellow  5 ppm                                                           yellow                                               59  F9     R2      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange orange yellow                                        60  F9     R3      strongly                                                                              almost strongly                                                                               5 ppm                                                    orange colorless                                                                             yellow                                        61  F9     R4      strongly                                                                              almost strongly                                                                               5 ppm                                                    red    colorless                                                                             yellow                                        62  F9     R5      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange orange yellow                                        63  F9     R6      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange orange yellow                                        64  F9     R7      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange orange yellow                                        65  F9     R8      orange weakly strongly                                                                               5 ppm                                                           orange yellow                                        66  F9     R9      strongly                                                                              weakly strongly                                                                              10 ppm                                                    bright yellow yellow                                                           red                                                         67  F9     R10     strongly                                                                              weakly strongly                                                                              10 ppm                                                    red    yellow yellow                                        68  F10    R1      strongly                                                                              almost strongly                                                                               5 ppm                                                    violet colorless                                                                             yellow                                        69  F10    R2      strongly                                                                              almost strongly                                                                               5 ppm                                                    violet colorless                                                                             yellow                                        70  F10    R3      strongly                                                                              almost strongly                                                                               5 ppm                                                    dark blue                                                                             colorless                                                                             yellow                                        71  F10    R4      strongly                                                                              weakly strongly                                                                               5 ppm                                                    green  green  yellow                                        72  F10    R5      strongly                                                                              weakly strongly                                                                               5 ppm                                                    violet red    yellow                                        73  F10    R6      strongly                                                                              almost strongly                                                                               5 ppm                                                    violet colorless                                                                             yellow                                        74  F10    R7      strongly                                                                              almost strongly                                                                               5 ppm                                                    bluish colorless                                                                             yellow                                                           gray                                                        75  F10    R8      strongly                                                                              almost strongly                                                                               5 ppm                                                    reddish                                                                               colorless                                                                             yellow                                                           violet                                                      76  F10    R9      strongly                                                                              weakly strongly                                                                               5 ppm                                                    red    yellow yellow                                        77  F10    R10     strongly                                                                              almost strongly                                                                               5 ppm                                                    violet colorless                                                                             yellow                                        78  F11    R1      strongly                                                                              almost strongly                                                                               5 ppm                                                    violet colorless                                                                             yellow                                        79  F11    R2      strongly                                                                              weakly strongly                                                                               5 ppm                                                    yellowish                                                                             yellow yellow                                                           orange                                                      80  F11    R3      strongly                                                                              almost strongly                                                                               5 ppm                                                    violet colorless                                                                             yellow                                        81  F11    R4      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange yellow yellow                                        82  F11    R5      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange yellow yellow                                        83  F11    R6      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange yellow yellow                                        84  F11    R7      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange yellow yellow                                        85  F11    R8      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange yellow yellow                                        86  F11    R9      strongly                                                                              weakly strongly                                                                               5 ppm                                                    red    yellow yellow                                        87  F11    R10     strongly                                                                              weakly strongly                                                                               5 ppm                                                    dark red                                                                              yellow yellow                                        88  F12    R1      strongly                                                                              almost strongly                                                                               5 ppm                                                    reddish                                                                               colorless                                                                             yellow                                                           violet                                                      89  F12    R2      strongly                                                                              almost strongly                                                                               5 ppm                                                    violet colorless                                                                             yellow                                        90  F12    R3      strongly                                                                              almost strongly                                                                               5 ppm                                                    violet colorless                                                                             yellow                                        91  F12    R4      strongly                                                                              almost strongly                                                                               5 ppm                                                    green  colorless                                                                             yellow                                        92  F12    R5      strongly                                                                              almost strongly                                                                               5 ppm                                                    reddish                                                                               colorless                                                                             yellow                                                           violet                                                      93  F12    R6      strongly                                                                              almost strongly                                                                               5 ppm                                                    dark blue                                                                             colorless                                                                             yellow                                        94  F12    R7      strongly                                                                              almost strongly                                                                               5 ppm                                                    reddish                                                                               colorless                                                                             yellow                                                           violet                                                      95  F12    R8      strongly                                                                              almost strongly                                                                               5 ppm                                                    bright colorless                                                                             yellow                                                           blue                                                        96  F12    R9      strongly                                                                              weakly strongly                                                                               5 ppm                                                    bright yellow yellow                                                           blue                                                        97  F12    R10     strongly                                                                              weakly strongly                                                                               5 ppm                                                    violet yellow yellow                                        98  F13    R1      strongly                                                                              weakly strongly                                                                               5 ppm                                                    yellowish                                                                             yellow orange                                                           brown                                                       99  F13    R2      strongly                                                                              weakly strongly                                                                               5 ppm                                                    reddish                                                                               yellow orange                                                           brown                                                      100  F13    R3      strongly                                                                              weakly strongly                                                                               5 ppm                                                    reddish                                                                               yellow orange                                                           violet                                                     101  F13    R4      strongly                                                                              weakly strongly                                                                               5 ppm                                                    yellow yellow orange                                       102  F13    R5      strongly                                                                              weakly strongly                                                                               5 ppm                                                    red    yellow orange                                       103  F13    R6      strongly                                                                              weakly strongly                                                                               5 ppm                                                    yellowish                                                                             yellow orange                                                           green                                                      104  F13    R7      yellowish                                                                             weakly strongly                                                                               5 ppm                                                    brown  yellow orange                                       105  F13    R8      greenish                                                                              weakly strongly                                                                               5 ppm                                                    gray   yellow orange                                       106  F13    R9      colorless                                                                             weakly strongly                                                                               5 ppm                                                           yellowish                                                                             orange                                                                  orange                                              107  F13    R10     strongly                                                                              weakly strongly                                                                               5 ppm                                                    reddish                                                                               yellow orange                                                           brown                                                      108  F14    R1      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange yellow yellow                                       109  F14    R2      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange yellow yellow                                       110  F14    R3      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange yellow yellow                                       111  F14    R4      strongly                                                                              weakly strongly                                                                               5 ppm                                                    yellow yellow yellow                                       112  F14    R5      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange yellow yellow                                       113  F14    R6      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange yellow yellow                                       114  F14    R7      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange yellow yellow                                       115  F14    R8      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange yellow yellow                                       116  F14    R9      strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange yellow yellow                                       117  F14    R10     strongly                                                                              weakly strongly                                                                               5 ppm                                                    orange yellow yellow                                       ______________________________________                                    

EXAMPLE 118 (Preparation of F7)

a) 42.6 g (0.04 mol) of m-aminoazotoluene hydrochloride (24.5% strength by weight) and 0.2 g of a wetting agent were suspended in 32 ml of water and 12 ml of 30% strength by weight hydrochloric acid. The suspension was then admixed with 20 g of ice, 7 ml of toluene and 12 ml of 23% strength by weight aqueous sodium nitrite solution and stirred at from 5 to 10° C. for 2 h.

b) 3..76 g (0.04 mol) of phenol and 100 ml of water were adjusted with 50% strength by weight sodium hydroxide solution to pH 6.4 and admixed at 0° C. with the diazonium salt solution described under a). The pH was held between 4 and 5 with 10% strength by weight sodium hydroxide solution. After stirring overnight the pH was reduced to 1.5 with 10% strength by weight hydrochloric acid and the precipitated solid was isolated.

Yield: 10.1 g

EXAMPLE 119 (Preparation of F9)

a) 3.0 g (0.02 mol) of methyl anthranilate were dissolved at 0° C. in 30 ml of water, 50 g of ice and 5 ml of concentrated hydrochloric acid and then admixed with 6 ml of 23% strength by weight aqueous sodium nitrite solution. The mixture was then stirred at from 0° to 5° C. for 30 minutes until a clear solution had formed.

b) 2.7 g (0.02 mol) of 2,3,6-trimethylphenol in 100 ml of water were adjusted with 50% strength by weight sodium hydroxide solution to pH 13 and admixed with the diazonium salt solution described under a). After stirring overnight the pH was reduced to 2.1 with 10% strength by weight hydrochloric acid and the precipitated solid was isolated.

Yield: 5.8 g

EXAMPLE 120 (Preparation of F12)

a) 7.19 g (0.05 mol) of p-nitroaniline and 0.1 g of a wetting agent were suspended in 45 ml of water and 17.5 ml of 30% strength by weight hydrochloric acid. The suspension was then admixed with 55 g of ice and 16.5 ml of 23% strength by weight aqueous sodium nitrite solution and stirred at from 0° to 5° C. for 1 h.

b) 7.56 g (0.05 mol) of 2-monoethylamino-4-methylphenol were added to 100 ml of water and adjusted with 50% strength by weight sodium hydroxide solution to pH 10. Then the diazonium salt solution described under a) was added at 5° C. The pH was held between 7 and 8 with 10% strength by weight sodium hydroxide solution. After stirring overnight the pH dropped to 4.6 and the precipitated solid was filtered off with suction.

Yield: 14.1 g

EXAMPLE 121 (Preparation of F13)

a) 53.3 g (0.05 mol) of m-aminoazotoluene hydrochloride (24.5% strength by weight) and 0.2 g of a wetting agent were suspended in 40 ml of water and 15 ml of 30% strength by weight hydrochloric acid. The suspension was then admixed with 25 g of ice, 8.4 ml of toluene and 15 ml of 23% strength by weight aqueous sodium nitrite solution and stirred at from 5 to 10° C. for 2 h.

b) 7.56 g (0.05 mol) of 2-monoethylamino-4-methylphenol were added to 100 ml of water and pH 10 was set with 50% strength by weight sodium hydroxide solution. Then the diazonium salt solution described under a) was added at 5° C. The pH was held between 7 and 8 with 10% strength by weight sodium hydroxide solution. After stirring overnight the pH was adjusted with hydrochloric acid to 1.5 and the precipitated solid was filtered off with suction.

Yield: 15.9 g

EXAMPLE 122 (Preparation of F14)

a) 42.6 g (0.04 mol) of m-aminoazotoluene hydrochloride (24.5% strength by weight) and 0.2 g of a wetting agent were suspended in 32 ml of water and 12 ml of 30% strength by weight hydrochloric acid. The suspension was then admixed with 20 g of ice, 7 ml of toluene and 12 ml of 23% strength by weight aqueous sodium nitrite solution and stirred at from 5 to 10° C. for 2 h.

b) 6.7 g (0.04 mol) of m-N,N-diethylaminophenol were added to 100 ml of water and pH 13.2 was set with 50% strength by weight sodium hydroxide solution. Then the diazonium salt solution described under a) was added at 5° C. The pH was held between 4 and 5 with 10% strength by weight sodium hydroxide solution. After stirring overnight the pH was reduced to 1.5 with 10% strength by weight hydrochloric acid and the precipitated solid was isolated.

Yield: 16 g

The same method gives the dyes F10 and F11. 

We claim:
 1. A method for detecting azo dye marked mineral oils by treating the marked mineral oil with an extractant comprising water, a solvent and a base, the azo dye transferring from the mineral oil into the aqueous phase, which comprises using as marker an azo dye of the formula I ##STR12## where ring A may be benzofused,m is from 1 to 4, X¹ is hydrogen, C₁ -C₄ -alkyl, cyano or nitro, X² is hydrogen, C₁ -C₄ -alkyl, cyano, nitro, C₁ -C₄ -alkoxy or C₁ -C₁₆ -alkoxycarbonyl, X³ is hydrogen, C₁ -C₄ -alkyl, cyano or C₁ -C₁₆ -alkoxycarbonyl, and X⁴ is hydrogen, hydroxyl, C₁ -C₈ -alkyl, which may be phenyl-substituted, C₁ -C₄ -alkoxy, amino, C₁ -C₄ -dialkylamino or C₁ -C₁₆ -monoalkylamino whose alkyl chain may be interrupted by from 1 to 3 oxygen atoms in the ether function,as solvent a partially or completely water-miscible organic solvent, and as base an alkali or alkaline earth metal hydroxide, an alkali metal carbonate or an ammonium compound of the formula ##STR13## where R¹, R², R³ and R⁴ are each independently of the others C₁ -C₁₆ -alkyl or benzyl.
 2. A method as claimed in claim 1, wherein the azo dye used has the formula Ia ##STR14## where m is from 1 to 4,X¹ is hydrogen, cyano or nitro, X² is hydrogen, C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy or C₁ -C₁₃ -alkoxycarbonyl, X³ is hydrogen or C₁ -C₄ -alkyl, and X⁴ is hydrogen or C₁ -C₈ -alkyl, which may be phenyl-substituted.
 3. A method as claimed in claim 1, wherein the azo dye used has the formula Ib ##STR15## where X¹ is hydrogen,X² is hydrogen, X³ is hydrogen or C₁ -C₄ -alkyl, X⁴ is hydrogen, C₁ -C₄ -alkyl, C₁ -C₄ -dialkylamino or C₁ -C₁₆ -monoalkylamino, X⁵ is hydrogen or C₁ -C₄ -alkyl, and X⁶ is hydrogen, C₁ -C₄ -alkyl or C₁ -C₄ -alkoxy,with the proviso that a) at least one of the three radicals X¹, X² and X³ is different from hydrogen, b) X² may also be cyano when X⁴ is C₁ -C₄ -dialkylamino, c) X² may also be C₁ -C₄ -alkoxycarbonyl when all the radicals X⁴, X⁵ and X⁶ are different from hydrogen, and d) one of the radicals X¹, X² or X³ may also be nitro when X⁴ is C₁ -C₁₆ -monoalkylamino and X⁶ is C₁ -C₄ -alkyl.
 4. A method as claimed in claim 1, wherein the base used is an alkali or alkaline earth metal hydroxide.
 5. A method of marking a mineral oil, comprising adding to said mineral oil an effective amount therefor consisting of an azo dye of the formula Ia ##STR16## where m is from 1 to 4,X¹ is hydrogen, cyano or nitro, X² is hydrogen, C₁ -C₄ -alkyl, C₁ -C₄ -alkoxy or C₁ -C₁₃ -alkoxycarbonyl, X³ is hydrogen or C₁ -C₄ -alkyl, and X⁴ is hydrogen or C₁ -C₄ -alkyl, which may be phenyl-substituted.
 6. A method as claimed in claim 5 where X⁴ is hydrogen or 1-phenylethyl.
 7. A method as claimed in claim 5 where X¹ is hydrogen, X² is methyl or C₁ -C₁₃ -alkoxycarbonyl, and X³ is hydrogen or methyl.
 8. A method as claimed in claim 5 of azo dyes conforming to the formula Ic ##STR17## where Y is C₇ -C₁₁ -alkyl.
 9. A method of marking a mineral oil, comprising adding to said mineral oil an effective amount therefor of an azo dye of the formula Ib ##STR18## where X¹ is hydrogen,X² is hydrogen, X³ is hydrogen or C₁ -C₄ -alkyl, X⁴ is hydrogen, C₁ -C₄ -alkyl, C₁ -C₄ -dialkylamino or C₁ -C₁₆ -monoalkylamino, X⁵ is hydrogen or C₁ -C₄ -alkyl, and X⁶ is hydrogen, C₁ -C₄ -alkyl or C₁ -C₄ -alkoxy,with the proviso that a) at least one of the three radicals X¹, X² and X³ is different from hydrogen, b) X² may also be cyano when X⁴ is C₁ -C₄ -dialkylamino, c) X² may also be C₁ -C₄ -alkoxycarbonyl when all the radicals X⁴, X⁵ and X⁶ are different from hydrogen, and d) one of the radicals X¹, X² or X³ may also be nitro when X⁴ is C₁ -C₁₆ -monoalkylamino and X⁶ is C₁ -C₄ -alkyl.
 10. Azo dyes of the formula II ##STR19## where Y¹ is hydrogen, or C₁ -C₄ -alkyl-substituted phenylazo,Y² is hydrogen, Y³ is hydrogen or C₁ -C₄ -alkyl, X⁴ is hydrogen, C₁ -C₄ -alkyl, C₁ -C₄ -dialkylamino or C₁₁ -C₁₆ -monoalkylamino, X⁵ is hydrogen or C₁ -C₄ -alkyl, and X⁶ is hydrogen, C¹ -C₄ -alkyl or C₁ -C₄ -alkoxy,with the proviso that a) at least one of the three radicals Y¹, Y² and Y³ is different from hydrogen, b) Y² may also be cyano when X⁴ is C₁ -C₄ -dialkylamino, c) Y² may also be C₁ -C₄ -alkoxycarbonyl when all the radicals X⁴, X⁵ and X⁶ are different from hydrogen, and d) one of the radicals Y¹, Y² or Y³ may also be nitro when X⁴ is C₁ -C₁₆ -monoalkylamino and X⁶ is C₁ -C₄ -alkyl. 